Air conditioners are devices that are arranged in bed rooms, living rooms, or business shops and adjust temperature, moisture, cleanness and air flow to maintain pleasant indoor environments.
Such air conditioners are generally classified into an integrated type or a separate type. In terms of functions, the integrated and separate types are the same. However, the integrated type air conditioner has cooling and heat radiating functions integrated and is installed on a wall or window in a house, and the separate type air conditioner has an indoor unit installed in a room to perform room cooling and heating and an outdoor unit installed outside the room to perform heat radiating and compressing functions, wherein the indoor and outdoor units separated from each other are connected to each other through a coolant pipe.
Meanwhile, an air conditioner uses a motor for a compressor and a motor control device for controlling the motor.
FIG. 1 is a circuit diagram illustrating a conventional motor control device of an air conditioner.
Referring to FIG. 1, the conventional motor control device of an air conditioner converts commercial AC power into DC power through a converter and converts the DC power into AC power of a predetermined frequency through an inverter to drive a motor in an air conditioner. The converter is controlled by a converter control unit and the inverter is controlled by an inverter control unit.
The converter is subjected to power factor correction and DC voltage boosting by a switching operation. However, since switching elements in the converter 110 perform high-speed switching, harmonic current occurs that flows into a system connected to a commercial AC power supply to influence other devices connected to the system. For preventing this, a separate EMI noise filter is sometimes provided at an input terminal connected to the commercial AC power supply.
Every country has its own procedure to regulate such harmonic current. In particular, the EU (European Union) specifies regulations on harmonic current of less than 16 A in EN 61000-3-2 and regulations on harmonic current of 16 A or more in 61000-3-12.